LUBRICANT FOR POWDER METALLURGY AND METAL POWDER COMPOSITIONS CONTAINING SAID LUBRICANT

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The technical field relates to a metal powder composition including a lubricant. More particularly, it relates to a particulate composite lubricant for powder metallurgy and to a process for producing a powder composition for powder metallurgy including the particulate composite lubricant.

BACKGROUND

[0002] In the Powder Metallurgy industry (PM industry), metal powders, such as iron-based powders, are used for production of components. More particularly, metal powder compositions are compacted in a die under high pressure into green compacts, the green compacts are then ejected from the die and sintered into sintered compacts. This near net shape technology enables the production of parts at a lower cost than other conventional methods such as machining.

[0003] The metal powder composition comprises a mixture of metal powders, lubricant, and, optionally, other additives. The powder metallurgy lubricants are generally different types of waxes, which are either ground or atomized into fine particles, and blended with metal powders, such as iron and steel powders. The lubricant reduces the inter-particular friction and the friction with the die wall during compaction and therefore improves densification, but also reduces friction with the die wall during the ejection of the part from the die. Furthermore, the lubricant is selected to promote the metal powder composition to flow adequately within the die cavity and also be malleable enough not to hinder the compaction process. There is a strong relationship between the mechanical properties and the final density of the parts. Consequently, lubricants which allow for higher densities to be attained have additional value. Commonly used lubricants for PM applications comprise metal stearates and amide waxes such as ethylene bisstearamide wax. Albeit being excellent lubricants, metal stearates can stain the parts during sintering and cause heavy metal contamination through the sintering furnace exhaust fumes.

[0004] US patent application no 2006/099104 to McCall et al. discloses a particulate lubricant including discrete particles of a fatty monoamide, especially oleamide, and discrete particles of at least one other powder metallurgy lubricant and, in an embodiment, a fatty bisamide. In another embodiment, the other powder metallurgy lubricant is a metal stearate. In combination, the fatty monoamide discrete particles and the at least one other powder metallurgy lubricant provide a synergistic free-flowing composition.

BRIEF SUMMARY OF THE INVENTION

[0005] It is therefore an aim of the present invention to address the above mentioned issues.

[0006] According to the invention, there is provided a particulate composite lubricant for powder metallurgy. The particulate composite lubricant comprises: first discrete particles comprising a fatty primary monoamide wax, being substantially free of fatty bisamide wax, and being at least partially coated with metal oxide nanoparticles, the at least partially coated first discrete particles having average particle size between 15 µm and 100 µm, and second metal-stearate free discrete particles comprising a fatty bisamide wax and having average particle size smaller than 50 µm.

[0007] In an embodiment, the at least partially coated first discrete particles have an average particle size between 25 µm and 75 µm.

[0008] In an embodiment, a D99 of the at least partially coated first discrete particles is between 80 µm and 220 µm.

[0009] In an embodiment, a D99 of the at least partially coated first discrete particles is between 115 µm and 180 µm.

[0010] In an embodiment, the second discrete particles have an average particle size smaller than 15 µm.

[0011] In an embodiment, a D99 of the second discrete particles is smaller than 200 µm.

[0012] In an embodiment, a D99 of the second discrete particles is smaller than 150 µm.

[0013] In an embodiment, the first discrete particles comprise at least 90 wt% of the fatty primary monoamide wax.

[0014] In an embodiment, the particulate composite lubricant comprises between 10 wt% and 60 wt% of the first discrete particles.

[0015] In an embodiment, the particulate composite lubricant comprises between 40 wt% and 90 wt% of the second discrete particles.

[0016] In an embodiment, the first discrete particles consist essentially of the fatty primary monoamide wax at least partially coated with the metal oxide nanoparticles.

[0017] In an embodiment, the first discrete particles consist of the fatty primary monoamide wax at least partially coated with the metal oxide nanoparticles.

[0018] In an embodiment, the second discrete particles further comprise at least 50 wt% of the fatty bisamide wax and less than 10 wt% of a fatty primary monoamide wax.

[0019] In an embodiment, the second discrete particles further comprise at least 90 wt% of the fatty bisamide wax.

[0020] In an embodiment, the second discrete particles consist essentially of the fatty bisamide wax.

[0021] In an embodiment, the second discrete particles are substantially metal free.

[0022] In an embodiment, the fatty primary monoamide wax is a monoamide of a fatty acid of 12 to 24 carbons. The monoamide can be selected from the group consisting of: lauramide, palmitamide, stearamide, arachidamide, behenamide, oleamide, erucamide, and combinations thereof.

[0023] In an embodiment, the metal oxide nanoparticles comprise at least one of iron oxides, TiO₂, Al₂O₃, SnO₂, SiO₂, CeO₂, and indium titanium oxide nanoparticles, and combinations thereof.

[0024] In an embodiment, the metal oxide nanoparticles comprise fumed silica nanoparticles.

[0025] In an embodiment, the first discrete particles comprises less than 5 wt% of metal oxide nanoparticles.

[0026] In an embodiment, the first discrete particles are smaller than 250 µm.

[0027] In an embodiment, the fatty bisamide wax is a fatty acid bisamide selected from the group consisting of: methylene bisoleamide, methylene bisstearamide, ethylene bisoleamide, hexylene bisstearamide, and ethylene bisstearamide (EBS), and mixtures thereof.

[0028] In an embodiment, the second discrete particles have an average particle size smaller than 50 µm.

[0029] In a particular embodiment, the first discrete particles comprise erucamide particles and the metal oxide nanoparticles comprise fumed silica nanoparticles and the second discrete particles comprise ethylene bisstearamide particles. The particular composite lubricant can comprise between 10 wt% and 60 wt% of the erucamide particles and between 40 wt% and 90 wt% of the ethylene bisstearamide particles. The erucamide particles can have an average particle size of 60 µm and a diameter smaller than 175 µm.

[0030] According to a further general aspect, there is provided a metallurgical powder composition, comprising a metal-based powder admixed with the particulate composite lubricant as described above in a concentration ranging between 0.1 wt% and 5 wt%. In an embodiment, the metal-based powder is an iron-based powder.

[0031] According to a further general aspect, there is provided a process for producing a powder composition for powder metallurgy. The process comprises: adding the particulate composite lubricant as described above in a concentration ranging between 0.1 wt% and 5 wt%, based on a total weight of the powder composition, to a metal-based powder. In an embodiment, the metal-based powder is an iron-based powder.

[0032] In this specification, a substance is a wax if it is kneadable at about 20 °C, is solid to brittle, has a coarse to microcrystalline structure, is translucent to opaque, not glassy, melts above 40 °C without decomposing, is slightly liquid (less viscous) just above the melting point, has a strongly temperature-dependent consistency and solubility, and is polishable under slight pressure.

[0033] In this specification, the term "composite" is intended to mean a combination of at least two components. The components can be melted or agglomerated together or provided as distinct discrete particles.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 

Figure 1 is a SEM micrograph of erucamide wax particles having a D99 of 175 µm and an average particle size of 63µm, coated with 0.5 wt% of fumed silica;

Figure 2 is a SEM micrograph of ethylene bisstearamide (EBS) wax particles having a D99 of 80 µm and an average particle size of 22 µm;

Figure 3 is a graph showing the green density as a function of the compacting pressure for three lubricants of example A;

Figure 4 is a graph showing the stripping pressure as a function of the compacting pressure for the three lubricants of example A;

Figure 5 is a graph showing the sliding pressure as a function of the compacting pressure for the three lubricants of example A;

Figure 6 is a graph showing the out-die sliding pressure as a function of the compacting pressure the three lubricants of example A;

Figure 7 is a graph showing the Hall flow rate for 30 minutes and 24 hours of blending followed by 24 hours of rest for two lubricants of example B; and

Figure 8 is a graph showing the Hall apparent density for 30 minutes and 24 hours of blending followed by 24 hours of rest for the two lubricants of example B.

DETAILED DESCRIPTION

[0035] In reference to the accompanying drawings, a particulate composite lubricant for a metal powder composition, such as and without being limitative, an iron-based powder composition will be described. The composite lubricant can act as a compaction aid and/or a pressing aid for the metal powder composition. The composite lubricant is based on fatty acid waxes.

[0036] In an embodiment, the particulate composite lubricant comprises a combination of first discrete particles including a fatty primary monoamide wax at least partially coated with metal oxide nanoparticles and second discrete particles including a fatty bisamide wax. The second discrete particles are free of metal-stearate and, in an embodiment, free of metal particles.

[0037] In an embodiment, the first discrete particles comprise at least about 90 wt% of the fatty primary monoamide wax. It is appreciated that the first discrete particles can comprise more than one fatty primary monoamide wax, i.e. a combination of fatty primary monoamide waxes. They are substantially free of fatty bisamide wax.

[0038] In an embodiment, the second discrete particles can include other component than the fatty bisamide wax. For instance, they can comprise a relatively small amount of a fatty primary monoamide wax. In an embodiment, the second discrete particles comprise at least about 50 wt% of the fatty bisamide wax and less than about 10 wt% of a fatty primary monoamide wax. In another embodiment, the second discrete particles can comprise at least about 90 wt% of the fatty bisamide wax and, for instance, less than about 1 wt% of fatty primary monoamide wax. It is appreciated that the second discrete particles can comprise more than one fatty bisamide wax, i.e. a combination of fatty bisamide waxes.

[0039] In an embodiment, the particulate composite lubricant comprises between about 10 wt% and about 60 wt% of the first discrete particles including the fatty primary monoamide wax at least partially coated with the metal oxide nanoparticles and, in another embodiment, between about 25 wt% and about 45 wt% of the first discrete particles. In an embodiment, the particulate composite lubricant comprises between about 40 wt% and about 90 wt% of the second discrete particles including the fatty bisamide wax and, in another embodiment, between about 55 wt% and about 75 wt% of the second discrete particles.

[0040] In an embodiment, the fatty primary monoamide wax is a monoamide of a fatty acid, saturated or unsaturated, of 12 to 24 carbons, which can be selected from the group comprising: lauramide, palmitamide, stearamide, oleamide, arachidamide, behenamide, erucamide, and combinations thereof.

[0041] Fatty primary monoamide waxes are hydrophilic molecules, due to the polarity of their amide function. Thus, substantially pure fatty primary monoamide wax particles tend to agglomerate over time, especially if they are exposed to higher humidity environments. When the fatty primary monoamide wax particles are admixed to metal powder, the exposure of the powder mix to relatively high humidity levels will cause the flow rate of the powder mix to deteriorate.

[0042] In order to counteract the hydrophilic nature of the fatty primary monoamide wax, a coating of metal oxide nanoparticles, such as and without being limitative fumed silica, can be applied on the fatty primary monoamide wax-based particles. This coating will insure a proper powder mix flow rate. In order for the metal oxides nanoparticles to protect the fatty primary monoamide wax against humidity, it must be coated superficially, i.e. adhered on the surface. The admixing of metal oxides nanoparticles to the metal powder blends, as often done to increase their flow properties, will not offer any protection against exposure to humid environments. Such blends tend to exhibit no flow in a Hall funnel.

[0043] The first discrete particles are at least partially coated with nanoparticles of at least one metal oxide. The metal oxide nanoparticles cover, at least partially, an outer surface of the fatty primary monoamide wax-based particles. The metal oxide nanoparticles can be iron oxides, TiO₂, Al₂O₃, SnO₂, SiO₂, CeO₂, and indium titanium oxide nanoparticles or combinations thereof. In an embodiment, the metal oxide nanoparticles comprise fumed silica nanoparticles. The nanoparticles are smaller than about 200 nm. In an embodiment, they are smaller than about 100 nm. In an embodiment, the primary particle size is between about 5 and 50 nm. In an embodiment, the metal oxide nanoparticle coating represents less than about 5 wt% of the weight of the primary discrete particles and, in another embodiment, less than about 2 wt%.

[0044] The at least partially coated discrete particles of the fatty primary monoamide wax are characterized by a diameter smaller than about 250 µm and having an average particle size between 15 µm and 100 µm and, in another embodiment, between about 25 µm and about 75 µm. In an embodiment, they are characterized by a D99 between about 80 µm and about 220 µm, i.e. 99 % of the particles are smaller than the D99, and, in another embodiment, between about 115 µm and about 180 µm.

[0045] In an embodiment, the fatty bisamide wax is a fatty acid bisamide which can be selected from the group consisting of methylene bisoleamide, methylene bisstearamide, ethylene bisoleamide, hexylene bisstearamide, and ethylene bisstearamide (EBS), and mixtures thereof.

[0046] In an embodiment, the second discrete particles are characterized by an average particle size smaller than 50 µm and, in another embodiment, smaller than about 15 µm. In an embodiment, they are characterized by a D99 smaller than about 200 µm and, in another embodiment, smaller than about 150 µm.

[0047] In an implementation, the composite lubricant comprises discrete particles of erucamide, as fatty primary monoamide wax, at least partially coated with fumed silica nanoparticles, as metal oxide, mixed with discrete particles of ethylene bisstearamide (EBS), as fatty bisamide wax. Erucamide is a fatty primary monoamide wax and, more particularly, a monounsaturated fatty acid based wax (C22:1) and EBS is a fatty bisamide wax. In an embodiment, the composite lubricant comprises between about 10 wt% and about 60 wt% of the erucamide particles at least partially coated with fumed silica nanoparticles. In an embodiment, the composite lubricant comprises between about 40 wt% and about 90 wt% of EBS.

[0048] In an implementation, the particles of erucamide are substantially spherical and have a larger diameter than the particles typically used as lubricant in powder metallurgy. More particularly, they are characterized by an average particle size of about 60 micrometer (µm) and their diameter is smaller than about 175 µm. For instance, the particles of the lubricant Acrawax® C, which is a typically used lubricant in powder metallurgy, are characterized by an average particle size of about 5 to 7 micrometer (µm) and their diameter is smaller than about 25 µm. Acrawax® C is an amide wax and, more particularly, a N,N'-ethylene bisstearamide.

[0049] Figure 1 is a SEM micrograph of erucamide wax particles having a D99 of 175 µm coated with 0.5% wt% of fumed silica which can be mixed with EBS wax particles to obtain the composite lubricant. Figure 2 is a SEM micrograph of EBS wax particles having a D99 of 80 µm, which can be combined with the particles shown in Figure 1.

[0050] In an embodiment, to manufacture the discrete particles of fatty primary monoamide wax at least partially coated with metal oxide nanoparticles, the lubricant particles can be prepared by melting the fatty primary amide wax, followed by a desintegration step, resulting in discrete particles, which are then at least partially coated with the metal oxide nanoparticles. The desintegration can be performed by atomisation of the melt by a gas or a liquid medium or through a combination of cooling down the melt until it is solidified and grinding the solidified mixture into discrete particles. The first discrete particles of fatty primary monoamide wax at least partially coated with metal oxide nanoparticles are then combined with the second discrete particles of fatty bisamide wax in predetermined proportions.

[0051] In some implementations, the composite lubricant including first discrete particles of fatty primary monoamide wax at least partially coated with metal oxide nanoparticles combined with the second discrete particles of fatty bisamide wax improved the ejection behavior by reducing the ejection forces, improved the flow properties, and showed an adequate resistance to humidity, compared with traditional powder metallurgy lubricants.

[0052] The above-described particulate composite lubricant can be mixed with a metal-based powder, such as and without being limitative, an iron-based powder to obtain a powder metallurgical composition. In an embodiment, the lubricant can be added in a concentration ranging between about 0.1 wt% and about 5 wt% of the powder metallurgical composition. In an embodiment, the concentration is less than about 2 wt% and, in another embodiment, between about 0.2 wt% and about 1 wt% of the powder metallurgical composition. The metal powder can be a metal powder mix including several types of metal powder mixed together or including only one type of metal powder. The metal powders can be iron-based metal powders suitable, for instance for medium range density parts (for instance, between 6.8 and 7.4 grams per cubic centimeter (g/cm³)). The metallurgical powder composition including the metal powder and the composite lubricant is used to manufacture compacted parts through powder metallurgy. The composite lubricant is typically added to the powder mix at the very end of the manufacturing process. The powder metallurgical composition can further include binders, processing aides, hard phases, machinability enhancing agents, and the like.

[0053] It will be appreciated that the methods described herein may be performed in the described order, or in any other suitable order.

[0054] It has been found that, in some implementations, the addition of Montan acid ester wax to the fatty amide wax improves the flowability and the apparent density of the powder metallurgical compositions containing same.

Example A

[0055] A first embodiment of the particulate composite lubricant of the invention will be described. The composite lubricant comprises a mixture of discrete particles of fatty monoamide wax partially coated with fumed silica nanoparticles and discrete particles of fatty bisamide wax. More particularly, it includes a mixture of erucamide, as fatty monoamide wax, and ethylene bisstearamide as fatty bisamide wax. In the composite lubricant, the concentration of fatty monoamide wax varies between about 10 wt% to about 60 wt%. In this example, substantially spherical-shaped erucamide particles were used produced by a melting, spray micronizing process and at least partially coated with 0.5 wt% fumed silica nanoparticles (Figure 1) to protect erucamide from the ambient humidity. The fumed silica coated particles were characterized with an average particle size of about 63 µm and all particles had a diameter smaller than about 250 µm.

[0056] In this example, all powder mixes were prepared using ATOMET 1001HP, a water-atomised steel powder, manufactured by Rio Tinto Metal Powders. Each was admixed with 1.8 wt% copper, 0.7 wt% natural graphite, and 0.7 wt% of a lubricant. The particulate composite lubricant tested in this example (Mix ID-1) included 40 wt% of erucamide particles coated with fumed silica nanoparticles and 60 wt% of Acrawax® C particles, as fatty bisamide wax.

[0057] Two iron-based powder mixes were used as benchmarks. A first one of the iron-based powder mixes contained Kenolube™ P11 (Mix ID-2) and a second one of the iron-based powder mixes contained atomized Acrawax® C (Mix ID-3). Kenolube™ P11 and Acrawax® C are commercially-available and well-known lubricants which are widely used in the PM industry. Acrawax® C is an amide wax and, more particularly, a N,N'-ethylene bisstearamide having a mean particle size of about 5-7 µm and Kenolube™ P11 is a composition of 22.5 wt% zinc stearate and 77.5 wt% of an amide wax. Table 1, below, describes the iron-based powder mixes that were evaluated for their compaction and ejection performance.

Table 1. Powder mixes used to determine the compaction and ejection behaviour of three lubricants.

Mix ID	Base Powder	Copper	Graphite	Lubricant
1	AT-1001 HP	1.8 wt%	0.7 wt%	0.7 wt% [0.28 wt% Coated Erucamide + 0.42 wt% Acrawax® C]
2 (Comparative)				Kenolube™ P11 0.7 wt%
3 (Comparative)				Acrawax® C 0.7 wt%

[0058] The apparent density and flow rate were measured using a Hall flow meter apparatus, according to MPIF Standard 4 and 3, respectively (MPIF, Standard Test Methods for Metal Powders and Powder Metallurgy Products - 2012 Edition, Princeton, NJ (USA): Metal Powder Industries Federation ; 2012, 150p.). The compaction and ejection behaviour were evaluated at the National Research Council Canada (Boucherville, Canada) on a 150 ton mechanical press. The press is equipped with strain gauges which can record the pressure applied on the top and bottom punch throughout the entire compaction and ejection process. 12.7mm height rings of 25.4 mm across with a core pin diameter of 14.2 mm were compacted at 5 parts per minute on a tungsten carbide die. The parts had an M/Q ratio of 4.54, while a standard TRS bar made according to MPIF standard 60 has an M/Q ratio of about 1.4. In order to obtain complete compressibility curves, parts were pressed at four compaction pressures of 485, 620, 715 and 825 MPa.

[0059] Results, shown in Table 2, below, and in Figures 3 to 6 showed similar compressibility for the Mix ID-1 than Acrawax® C (Mix ID-3) and Kenolube™ P11 (Mix ID-2). Ejection performances for Mix ID-1 were similar to Kenolube™ P11 (Mix ID-2), but significantly better than Acrawax® C (Mix ID-3).

Table 2. Results for the powder mixes detailed in Table 1.

Mix ID	Compaction Pressure (tsi)	Green Density (g/cc)	Stripping Pressure (tsi)	Sliding Pressure (tsi)	Out of Die Sliding Pressure (tsi)
1	35.5	6.96	0.90	0.82	0.75
	45.4	7.12	1.00	0.91	0.80
	51.7	7.18	0.98	0.87	0.76
	59.4	7.22	0.93	0.80	0.67
2 (Comparative)	35.7	7.00	0.88	0.78	0.68
	44.5	7.14	0.96	0.86	0.75
	52.3	7.22	0.91	0.81	0.69
	59.3	7.25	0.89	0.78	0.66
3 (Comparative)	35.8	6.97	0.96	0.87	0.76
	45.6	7.15	1.17	1.07	0.94
	53.0	7.19	1.19	1.09	0.97
	59.5	7.23	1.20	1.09	0.94

Example B

[0060] In this example, the resistance of two iron-based powder mixes to warm and humid environments was measured according to a procedure established in Thomas et al. (2009) (Thomas, Y.; St-Laurent, S.; Pelletier, S.; Gélinas, C. In Effect of Atmospheric Humidity and Temperature on the Flowability of Lubricated Powder Metallurgy Mixes, Advances in Powder Metallurgy & Particulate Materials, Las Vegas, June 28-July 1, 2009; MPIF, Princeton, NJ, USA.). Samples based on an AT-1001HP base powder and containing 0.6 wt% of natural graphite, 0.3 wt% MnS and 0.8 wt% of lubricant were prepared. The mixes are described in Table 3, below.

Table 3. Description of the powder mixes used to evaluate the resistance to humidity.

Mix ID	Base Powder	Graphite	MnS	Lubricant
4	AT-1001 HP	0.6 wt% F25	0.3 wt% Arcmetal	0.8 wt% [0.32 wt% Coated Erucamide + 0.48 wt% Acrawax® C]
5 (Comparative)				Kenolube™ 0.8 wt%
6 (Comparative)				0.8 wt% [0.32 wt% non-coated Erucamide + 0.48 wt% Acrawax® C] + fumed silica added to the metal powder mix

[0061] Highly hygroscopic lubricants would not flow after the conditioning period whereas non-hygroscopic lubricants are expected to maintain their flow behaviour. To perform this test, samples of 1 kilogram (kg) of the iron-based powder mixes were placed in a Blue M climate-controlled chamber which is equipped with a small V-type blender. Each powder blend was placed in the blender which was left open for an approximate period of one hour. This time span is necessary for the powder mixes to reach equilibrium with its surrounding environment. For this test, the chamber was set at a temperature of 60 °C and 60% RH. After this period, the blender was closed and the powder mixes blended for 30 minutes, after which a sample was collected. After the sampling was completed, the blender was turned on for a period of 24 hours. Once this period was over, another sample was taken. The flow rate and apparent density were measured on the first sample (taken out after 30 minutes of blending time). The last sample was also measured after a 24 h rest period.

[0062] Results are shown in Figures 7 and 8. Both lubricants in Mixes ID-4 and ID-5 had a good Hall flow rate following a short exposure to a warm and humid atmosphere. This was not the case for Mix ID-6 which already showed no measurable flow. This indicates that the admixing of fumed silica to the powder mix cannot protect it against the exposure to humid environments. On the other hand, after a longer exposure to humidity, Mix ID-4 is the only mix that flows indicating the benefits of using the erucamide particles coated with the fumed silica. Regarding apparent density, slightly higher values were obtained for Mix ID-4 while a significant reduction of apparent density was observed for Mix ID-5 after a long exposure to a humid atmosphere. The coated erucamide consequently offers a good protection against humidity exposure.

[0063] Several alternative embodiments and examples have been described and illustrated herein. The embodiments of the invention described above are intended to be exemplary only. A person of ordinary skill in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the scope of the claims. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while the specific embodiments have been illustrated and described, numerous modifications come to mind. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.

Claims

1. A particulate composite lubricant for powder metallurgy comprising: first discrete particles comprising a fatty primary monoamide wax and being substantially free of fatty bisamide wax, and second metal-stearate free discrete particles comprising a fatty bisamide wax, the particulate composite lubricant being characterized in that the fatty primary monoamide wax are at least partially coated with metal oxide nanoparticles, the at least partially coated first discrete particles having average particle size between 15 µm and 100 µm and the second metal-stearate free discrete particles have an average particle size smaller than 50 µm.

2. The particulate composite lubricant as claimed in claim 1, wherein the at least partially coated first discrete particles have an average particle size between 25 µm and 75 µm or a D99 of the at least partially coated first discrete particles is between 80 µm and 220 µm, preferably, between 115 µm and 180 µm.

3. The particulate composite lubricant as claimed in one of claims 1 and 2, wherein the second discrete particles have an average particle size smaller than 15 µm, or a D99 of the second discrete particles is smaller than 200 µm, preferably smaller than 150 µm.

4. The particulate composite lubricant as claimed in any one of claims 1 to 3, wherein the first discrete particles comprise at least 90 wt% of the fatty primary monoamide wax.

5. The particulate composite lubricant as claimed in any one of claims 1 to 4, wherein the particulate composite lubricant comprises between 10 wt% and 60 wt% of the first discrete particles and between 40 wt% and 90 wt% of the second discrete particles.

6. The particulate composite lubricant as claimed in any one of claims 1 to 5, wherein the first discrete particles consist essentially of the fatty primary monoamide wax at least partially coated with the metal oxide nanoparticles.

7. The particulate composite lubricant as claimed in any one of claims 1 to 6, wherein the second discrete particles further comprise at least 50 wt% of the fatty bisamide wax and less than 10 wt% of a fatty primary monoamide wax and, preferably, the second discrete particles further comprise at least 90 wt% of the fatty bisamide wax.

8. The particulate composite lubricant as claimed in any one of claims 1 to 7, wherein the second discrete particles consist essentially of the fatty bisamide wax and, preferably, the second discrete particles are substantially metal free.

9. The particulate composite lubricant as claimed in any one of claims 1 to 8, wherein the fatty primary monoamide wax is a monoamide of a fatty acid of 12 to 24 carbons and, preferably, the monoamide is selected from the group consisting of: lauramide, palmitamide, stearamide, arachidamide, behenamide, oleamide, erucamide, and combinations thereof.

10. The particulate composite lubricant as claimed in any one of claims 1 to 9, wherein the metal oxide nanoparticles comprise at least one of iron oxides, TiO₂, Al₂O₃, SnO₂, SiO₂, CeO₂, and indium titanium oxide nanoparticles, and combinations thereof and, preferably, the metal oxide nanoparticles comprise fumed silica nanoparticles.

11. The particulate composite lubricant as claimed in any one of claims 1 to 10, wherein the first discrete particles comprises less than 5 wt% of metal oxide nanoparticles.

12. The particulate composite lubricant as claimed in any one of claims 1 to 11, wherein the fatty bisamide wax is a fatty acid bisamide selected from the group consisting of: methylene bisoleamide, methylene bisstearamide, ethylene bisoleamide, hexylene bisstearamide, and ethylene bisstearamide, and mixtures thereof or the fatty bisamide wax of the second discrete particles comprises at least two fatty bisamide waxes.

13. The particular composite lubricant as claimed in claim 1, wherein the first discrete particles comprise erucamide particles and the metal oxide nanoparticles comprises fumed silica nanoparticles and the second discrete particles comprises ethylene bisstearamide particles and, preferably, the particular composite lubricant comprises between 10 wt% and 60 wt% of the erucamide particles and between 40 wt% and 90 wt% of the ethylene bisstearamide particles.

14. The particular composite lubricant of claim 13, wherein the erucamide particles have an average particle size of 60 µm and a diameter smaller than 175 µm.

15. A metallurgical powder composition, comprising a metal-based powder, preferably an iron-based powder, admixed with the particulate composite lubricant as claimed in any one of claims 1 to 14 in a concentration ranging between 0.1 wt% and 5 wt% based on a total weight of metallurgical powder composition.

16. A process for producing a powder composition for powder metallurgy, comprising:

adding the particulate composite lubricant as claimed in any one of claims 1 to 14 in a concentration ranging between 0.1 wt% and 5 wt%, based on a total weight of the powder composition, to a metal-based powder, preferably an iron-based powder.

Ansprüche

1. Partikuläres Kompositschmiermittel für Pulvermetallurige, umfassend: erste diskrete Partikel, die ein primäres Fettmonoamidwachs umfassen, und im Wesentlichen frei von einem Fettbisamidwachs sind, und zweite metallstearatfreie diskrete Partikel, die ein Fettbisamidwachs umfassen, wobei das partikuläre Kompositschmiermittel dadurch gekennzeichnet ist, dass das primäre Fettmonoamidwachs zumindest teilweise mit Metalloxidnanopartikeln beschichtet ist, wobei die zumindest teilweise beschichteten ersten diskreten Partikel eine durchschnittliche Partikelgröße zwischen 15 µm und 100 µm aufweisen und die zweiten metallstearatfreien diskreten Partikel eine durchschnittliche Partikelgröße von kleiner als 50 µm aufweisen.

2. Partikuläres Kompositschmiermittel nach Anspruch 1, wobei die zumindest teilweise beschichteten ersten diskreten Partikel eine durchschnittliche Partikelgröße zwischen 25 µm und 75 µm oder ein D99 der zumindest teilweise beschichteten ersten diskreten Partikel zwischen 80 µm und 220 µm, vorzugsweise zwischen 115 µm und 180 µm liegt.

3. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 und 2, wobei die zweiten diskreten Partikel eine durchschnittliche Partikelgröße von kleiner als 15 µm aufweisen oder ein D99 der zweiten diskreten Partikel kleiner als 200 µm, vorzugsweise kleiner als 150 µm ist.

4. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 bis 3, wobei die ersten diskreten Partikel mindestens 90 Gew.-% von dem primären Fettmonoamidwachs umfassen.

5. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 bis 4, wobei das partikuläre Kompositschmiermittel zwischen 10 Gew.-% und 60 Gew.-% von den ersten diskreten Partikeln und zwischen 40 Gew.-% und 90 Gew.-% von den zweiten diskreten Partikeln umfasst.

6. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 bis 5, wobei die ersten diskreten Partikel im Wesentlichen aus dem primären Fettmonoamidwachs bestehen, das zumindest teilweise mit den Metalloxidnanopartikeln beschichtet ist.

7. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 bis 6, wobei die zweiten diskreten Partikel ferner mindestens 50 Gew.-% von dem Fettbisamidwachs und weniger als 10 Gew.-% von einem primären Fettmonoamidwachs umfassen und wobei vorzugsweise die zweiten diskreten Partikel ferner mindestens 90 Gew.-% von dem Fettbisamidwachs umfassen.

8. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 bis 7, wobei die zweiten diskreten Partikel im Wesentlichen aus dem Fettbisamidwachs bestehen und vorzugsweise die zweiten diskreten Partikel im Wesentlichen metallfrei sind.

9. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 bis 8, wobei das primäre Fettmonoamidwachs ein Monoamid von einer Fettsäure mit 12 bis 24 Kohlenstoffatomen ist und wobei vorzugsweise das Monoamid aus der Gruppe ausgewählt ist, bestehend aus: Lauramid, Palmitamid, Stearamid, Arachidamid, Behenamid, Oleamid, Erucamid und Kombinationen davon.

10. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 bis 9, wobei die Metalloxidnanopartikel mindestens eines aus Eisenoxid, TiO₂, Al₂O₃, SnO₂, SiO₂, CeO₂ und Indiumtitanoxidnanopartikeln und Kombinationen davon umfassen und wobei vorzugsweise die Metalloxidnanopartikel pyrogene Kieselsäurenanopartikel umfassen.

11. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 bis 10, wobei die ersten diskreten Partikel weniger als 5 Gew.-% der Metalloxidnanopartikel umfassen.

12. Partikuläres Kompositschmiermittel nach einem der Ansprüche 1 bis 11, wobei das Fettbisamidwachs ein Fettsäurebisamidwachs ist, das aus der Gruppe ausgewählt ist, bestehend aus: Methylenbisoleamid, Methylenbisstearamid, Ethylenbisoleamid, Hexylenbisstearamid und Ethylenbisstearamid und Mischungen davon oder das Fettbisamidwachs der zweiten diskreten Partikel mindestens zwei Fettbisamidwachse umfasst.

13. Partikuläres Kompositschmiermittel nach Anspruch 1, wobei die ersten diskreten Partikel Erucamidpartikel umfassend, und die Metalloxidnanopartikel pyrogene Kieselsäurenanopartikel umfassen, und die zweiten diskreten Partikel Ethylenbisstearamidpartikel umfassen und wobei vorzugsweise das partikuläre Kompositschmiermittel zwischen 10 Gew.-% und 60 Gew.-% von den Erucamidpartikel und zwischen 40 Gew.-% und 90 Gew.-% von den Ethylenbisstearamidpartikel umfasst.

14. Partikuläres Kompositschmiermittel nach Anspruch 13, wobei die Erucamidpartikel eine durchschnittliche Partikelgröße von 60 µm und einen Durchmesser von kleiner als 175 µm aufweisen.

15. Metallurgische Pulverzusammensetzung, umfassend ein metallbasiertes Pulver, vorzugsweise ein eisenbasiertes Pulver, vermischt mit dem partikulären Kompositschmiermittel nach einem der Ansprüche 1 bis 14, und zwar in einer Konzentration zwischen 0,1 Gew.-% und 5 Gew.-% auf Basis von einem Gesamtgewicht der metallurgischen Pulverzusammensetzung.

16. Verfahren zum Herstellen von einer Pulverzusammensetzung für Pulvermetallurgie, umfassend:

Zugeben zu einem metallbasierten Pulver, vorzugsweise einem eisenbasierten Pulver, von dem partikulären Kompositschmiermittel nach einem der Ansprüche 1 bis 14 in einer Konzentration zwischen 0,1 Gew.-% und 5 Gew.-% auf Basis von einem Gesamtgewicht der Pulverzusammensetzung.

Revendications

1. Lubrifiant composite particulaire pour la métallurgie des poudres, comprenant : des premières particules discrètes qui comprennent une cire monoamide primaire grasse et qui sont substantiellement dépourvues de cire bisamide grasse, et des secondes particules discrètes dépourvues de stéarate de métal et comprenant une cire bisamide grasse, le lubrifiant composite particulaire étant caractérisé en ce que la cire monoamide primaire grasse est au moins partiellement enrobée avec des nanoparticules d'oxyde métallique, lesdites premières particules discrètes au moins partiellement enrobées ayant une taille moyenne de particule comprise entre 15 µm et 100 µm, et les secondes particules discrètes dépourvues de stéarate métallique ayant une taille moyenne de particule plus petite que 50 µm.

2. Lubrifiant composite particulaire tel que revendiqué dans la revendication 1, dans lequel lesdites premières particules discrètes au moins partiellement enrobées ont une taille moyenne de particule comprise entre 25 µm et 75 µm ou un D99 desdites premières particules discrètes au moins partiellement enrobées est compris entre 80 µm et 220 µm, de préférence compris entre 115 µm et 180 µm.

3. Lubrifiant composite particulaire tel que revendiqué dans l'une des revendications 1 et 2, dans lequel les secondes particules discrètes ont une taille moyenne de particule plus petite que 15 µm, ou un D99 des secondes particules discrètes est plus petit que 200 µm, de préférence plus petit que 150 µm.

4. Lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 3, dans lequel les premières particules discrètes comprennent au moins 90 % en poids de la cire monoamide primaire grasse.

5. Lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 4, dans lequel le lubrifiant composite particulaire comprend entre 10 % en poids et 60 % en poids des premières particules discrètes et entre 40 % en poids et 90 % en poids des secondes particules discrètes.

6. Lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 5, dans lequel les premières particules discrètes consistent essentiellement dans la cire monoamide primaire au moins partiellement enrobée avec les nanoparticules d'oxyde métallique.

7. Lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 6, dans lequel les secondes particules discrètes comprennent en outre au moins 50 % en poids de la cire bisamide grasse et moins de 10 % en poids d'une cire monoamide primaire grasse et, de préférence, les secondes particules discrètes comprennent en outre au moins 90 % en poids de la cire bisamide grasse.

8. Lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 7, dans lequel les secondes particules discrètes consistent essentiellement dans la cire bisamide grasse et, de préférence, les secondes particules discrètes sont substantiellement dépourvues de métal.

9. Lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 8, dans lequel la cire monoamide primaire grasse est un monoamide d'un acide gras ayant 12 à 24 carbones et, de préférence, le monoamide est sélectionné à partir du groupe consistant dans : lauramide, palmitamide, stéaramide, arachidamide, béhénamide, oléamide, érucamide, et des combinaisons de ceux-ci.

10. Lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 9, dans lequel les nanoparticules d'oxyde métallique comprennent des nanoparticules d'au moins l'un des oxydes de fer, de TiO₂, de Al₂O₃, de SnO₂, de SiO₂, de CeO₂, et d'oxyde de titane et d'indium, et des combinaisons de ceux-ci, et, de préférence, les nanoparticules d'oxyde métallique comprennent des nanoparticules de silice pyrogénée.

11. Lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 10, dans lequel les premières particules discrètes comprennent moins de 5 % en poids de particules d'oxyde métallique.

12. Lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 11, dans lequel la cire bisamide grasse est un bisamide d'acide gras sélectionné à partir du groupe consistant dans : bisoléamide de méthylène, bistéaramide de méthylène, bisoléamide d'éthylène, bistéaramide d'hexylène, et bistéaramide d'éthylène, et des mélanges de ceux-ci, ou la cire bisamide grasse des secondes particules discrètes comprend au moins deux cires bisamide grasses.

13. Lubrifiant composite particulaire tel que revendiqué dans la revendication 1, dans lequel les premières particules discrètes comprennent des particules d'érucamide et les nanoparticules d'oxyde métallique comprennent des nanoparticules de silice pyrogénée, et les secondes particules discrètes comprennent des particules de bistéaramide d'éthylène, et, de préférence, le lubrifiant composite particulaire comprend entre 10 % en poids et 60 % en poids des particules d'érucamide et entre 40 % en poids et 90 % en poids des particules de bistéaramide d'éthylène.

14. Lubrifiant composite particulaire de la revendication 13, dans lequel les particules d'érucamide ont une taille moyenne de particule de 60 µm et un diamètre plus petit que 175 µm.

15. Composition métallurgique en poudre, comprenant une poudre à base de métal, de préférence une poudre à base de fer, mélangée avec le lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 14 selon une concentration s'étendant entre 0.1 % en poids et 5 % en poids sur la base d'un poids total de la composition métallurgique en poudre.

16. Procédé pour produire une composition en poudre pour la métallurgie des poudres, comprenant :

ajouter le lubrifiant composite particulaire tel que revendiqué dans l'une quelconque des revendications 1 à 14 selon une concentration comprise entre 0.1 % en poids et 5 % en poids, sur la base d'un poids total de la composition en poudre, à une poudre à base de métal, de préférence une poudre à base de fer.

Drawing